Capacitor components are often used as passive electronic devices in integrated circuits (IC) such as radio frequency IC, monolithic microwave IC, etc. Common capacitor components include metal-oxide-semiconductor (MOS) capacitors, PN junction capacitors and MIM (metal-insulator-metal) capacitors. In some specific applications, MIM capacitors provide better electrical characteristics than MOS capacitors and PN junction capacitors. MOS capacitors and PN junction capacitors may be limited by their structures, and vacancy layers can be easily formed at the electrodes during operation. This may cause reduction of frequency characteristics. In contrast, MIM capacitors can provide better frequency and temperature characteristics. In semiconductor manufacturing, MIM capacitors can be formed by interlayer metal and copper interconnect processes, which reduces difficulties and complexities for integration in CMOS front-end processes.
FIG. 1 depicts an MIM capacitor made by a conventional CMOS IC manufacturing process. The MIM capacitor includes a substrate 100, a conductive layer 103 disposed within the substrate 100, and a dielectric layer 101 disposed on the substrate 100. The dielectric layer 101 has an opening exposing the surface of the conductive layer 103. The MIM capacitor further includes a first metal layer 103, an insulating layer 104, and a second metal layer 105. The first metal layer 103 is formed on the bottom and sidewall of the opening and serves as a first electrode plate of the MIM capacitor. The insulating layer 104 is formed on the surface of the first metal layer 103 and serves as a dielectric layer of the MIM capacitor. The second metal layer 105 is formed on the surface of the insulating layer 104 to fill the opening. The second metal layer 105 serves as a second electrode plate of the MIM capacitor.
During operation of the MIM capacitor, operating voltages are applied only to the conductive layer 103 and the second metal layer 105. However, such MIM capacitor is prone to leakage current during operation, which affects the stability of MIM capacitors.